Human monocytes are normal cells with numerous immunologic functions which have potential roles for preventing new tumors or eradicating established malignancies. Studies have been performed which have allowed us to establish a group of highly immunologically characterized normal human donors, to be used for a longitudinal analysis of the function of normal human monocytes and other components of the immune response. Investigations have particularly focused on the potential antitumor functions of normal human monocytes. We have been able to isolate large numbers of sterile human monocytes by elutriation and subsequently cryopreserve them in suspension, retaining function in the MIF, tumor growth inhibition, and several other assays of monocyte function. We developed methodology for separating human monocytes into subsets by size and density and have detected a monocyte subset with enhanced cytotoxic function and another subset with enhanced interferon production capabilities. We have performed several in-depth analyses into the genetic basis for human monocyte function using state-of-the-art genetic engineering methodologies and have documented elevation of monocyte total and messenger RNA following the activation to fibroblast growth factor (FGF) synthesis, but not interferon synthesis.